(1) Field of the Invention
The present invention relates to a semiconductor laser device having an oscillation wave length in the short wave length region.
(2) Description of the Prior Art
Visualization by a semiconductor laser device is expected as a device capable of utilizing practically a small-size high-efficiency light source instead of a conventional He-Ne gas laser device in fields of optical information processing devices, video disks and the like.
Typical instances of semiconductor laser devices heretofore proposed are as follows.
(1) A device using GaAlAs for an active layer and a cladding layer, proposed by, for example, I. Landany and H. Kressel in 1976 IEDM Technical Digest. PA1 (2) A device using GaAsP for an active layer and GaInP for a cladding layer, proposed by, for example, H. Kressel et al. in Applied Physics Letters, Vol. 30, No. 5, 1977, pages 249-251.
In the conventional device (1), the oscillation wave length is above 710 nm in a case of continuous oscillation at room temperature, and in the conventional device (2), the oscillation wave length is above 700 nm in a case of continuous oscillation at room temperature. In other words, continuous oscillation at room temperature is impossible at an oscillation wave length below the above critical level. The reason is that in order to obtain practical oscillation, it is required that the band gap of the active layer should be sufficiently smaller than that of the cladding layer and a direct transition area should be formed.